AngularJS interceptor

intercept.js

import { Injectable, Injector } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs/Rx';
import 'rxjs/add/observable/throw'
import 'rxjs/add/operator/catch';

@Injectable()
export class MyHttpInterceptor implements HttpInterceptor {
  constructor() { }

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    console.log("intercepted request ... ");

    // Clone the request to add the new header.
    const authReq = req.clone({ headers: req.headers.set("headerName", "headerValue")});

    console.log("Sending request with new header now ...");

    //send the newly created request
      return next.handle(authReq)
                .catch((error, caught) => {
            return Observable.throw(error);
        }) as any;
  }
}